Feeding device for grinding cylinder-mills



E. ROTH. FEEDING DEVICE FOR GRINDING CYLINDER MILLS.

, APPLICATION FILEDBIAR. 4, I919. 1,337,567.

Patented Apr. 20, 1920 ZSHEETS-SHEET l- UNITED STATES PATENT OFFICE.

ERNST ROTH, OF NIEDER-UZWIL, SWITZERLAND.

FEEDING DEVICE FOR GRINDING CYLINDER-MILLS.

Application filed March 4, 1919.

of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters or figures of reference marked thereon,

which form a part of this specification.

It is the general endeavor to design grinding cylinder mills so that the material is fed to the grinding stones in a very uniform manner. To this end there have been proposed a great number of very different constructions. According to one of these constructions already proposed, a feed-roll arranged below the feeding hopper supplies the material to a second feedroll which then carries the material further into the entrance angle provided between the cylindrical millstones. In order to obtain in this construction a uniform feed, a sliding bridge is arranged between the two feed-rolls, so that the material passes from the first feedroll over said bridge onto the second feedroll. The latter conveys then continually a certain quantity of material from said bridge into the small passage provided between the two millstones. It has also been proposed to provide in combination with the first feed-roll a feedplate adapted to be adjusted in accordance with the quantity of grinding material contained in the feeding hopper, in order to vary the feeding aperture provided between the lower endof the feed-plate and the first feed-roll. As this feeding aperture becomes however easily clogged, it has further been proposed to provide at the lower end of the feedplate a small roll adapted to remove the clogging, thus preventing any irregular supply of the material to the cylindrical millstones. baid roll has the task to draw the material to be ground into the feeding aperture provided between said roll and the first feed-roll.

Although the first feed roll is adapted to uniformly convey the material'to be ground, the current of material leaving this feed-roll can usually not be supplied to the grinding stones, as the material has to be supplied to the millstone in the form of a very uni- Specification of Letters Patent.

Patented Apr. 20, 1920.

Serial No. 280,516.

form veil-like, thin layer or sheet. In order to obtain such a thin layer, different constructions have also been proposed. Thus, for instance, it has been proposed to cause the first feed-roll to deliver the material to a sliding plate from which it falls onto a second sliding plate where it is reduced to dust; the latter is then thrown into the entrance space provided between the two grinding stones by the second feed-roll. This arangement has however the drawback, that the material to be ground does notleave the sliding plate in small particles but in pieces having a certain size, as the small particles of the material to be supplied to the millstones have the tendency to stick together owing to their adhesion. In consequence of this, the feed is not uniform and this can not be remedied by the lower feed-roll; clouds will therefore appear in the feeding sheet on its way from the lower feed-roll to the millstones indicating that the feed is not uniform.

Any clogging occurring in the feeding aperture has the effect of producing tears or spaces in the thin feeding layer. Notwithstanding the most different experiments carried out, it has not yet been possible to design a feeding device for grinding cylinder mills adapted to produce under all circumstances a uniform, uninjured feeding sheet of material to be ground, and to supply it in this state to the millstones.

This invention relates now to a feeding device for grinding cylinder mills adapted to produce such a uniform, uninjured feeding sheet. The feeding device according to the present invention comprises a feed-roll cooperating with a slowly rotating auxiliary roll provided at the lower end of a feedplate and conveying the material to an in clined bridge across which the grain slides and which cooperates at its lower end with a second feed-roll running at a greater speed than said first mentioned feed-roll. This second feed-roll takes off the material directly from the bridge and discharges it in the shape of a uniform, uninjured thin layer or film into the entrance space or nip between the millstones.

This invention will now be more partic ularly described with reference to the accompanying drawings illustrating by way of example one construction of carrying out the invention. In these drawings:

Figure 1 is a vertical cross-section partly on the line I-I and partly on the line IVIV of F ig. 2 through a grinding cylinder mill fitted with the new feeding device.

Fig. 2 is a section on the line IIII of Fig. 1 and Fig. 3 a section on the line IIIIII of F i 2.

Fig. 4 shows details of the grinding cylinder mill on an enlarged scale.

Referring to the drawings, 8 denotes a feeding channel separated at its lower end by a feed-plate 9 from the space 11 in which are arranged the two millstones 7. The feed-plate 9 is connected to journals 10 .pivotally mounted in the casing 12 forming a portion of the grinding cylinder mill. 13 denotes means for adjusting the plate 9 and consequently also the journals 10 connected to said plate 9. The lower end'of the feedplate 9 cooperates with an auxiliary roll 1 which cooperates also with a ribbed or toothed roll 2 and is spaced therefrom by the adjusting means 13 in accordance with the size of the grain to be fed. The roll 1 is supported in said journals 10, the bearings for said roll 1 in the journals 10 being arranged eccentrically with regard to the axis of rotation of the journals 10. Upon the roll 2 rests one end of an adjustable bridge 5 across which the grain is caused to slide the angle of inclination of which is less than the angle of repose of the material to be ground, so that the material having the form of a thin sheet is prevented from sliding down said bridge 5 in an irregular manner. The lower end of the bridge 5 rests upon a second discharge feed-roll 3 running at a higher speed than the feed-roll 2 and taking off the material to be ground directly from the lower end of the bridge 5 and discharging from the feeding mechanism to the grinding rolls. The plane passing through the axes of the two feed-rolls 2 and 3 is parallel to the upper surface of the bridge 5. 15 denotes the main driving pulley of the grinding mill fixed to a shaft 16.. A'

toothed-wheel gearing 17 transmits the drive to the roll 3. The rotary motion of the latter is transmitted to the roll 2 by means of atoothed-wheel gearing 18 (Fig. 3) and also to the auxiliary roll 1 by means of a worm gearing 19 (Figs. 2 and 1).

The ribbed roll 2 rotates with a meanvelocity and conveys the material falling into the spaces provided between its ribs to the sliding bridge 5. Thus, it will be seen, that strips of material to be ground are successively delivered to said bridge 5.

Owing to the sliding of the material occurring on the bridge 5, the rows of material transverse of the direction of movement of the material conveyed by the recesses provided between the ribs of the feed-roll 2 are caused toshift nearer together; at the end of the bridge 5 they are then situated so The feed is therefore acontinuous one over the whole length of the feed-rolls until any foreign body that can not be drawn into the entrance angle by the feed-roll 2 alone, is ammed between the auxiliary roll 1 and the feed-roll 2.

Any foreign body conveyed into the entrance angle between the auxiliary roll 1 and the feed-roll 2 and jammed between these rolls will produce an interruption in the feed-layer so that a space or tear will appear in the sheet of material on the bridge 5. As the auxiliary roll 1 is caused to rotate slowly and is not kept stationary, said foreign body is seized by the auxiliary roll 1 and the feed-roll 2 and conveyed forward so that only a transitory interruption in the feed will \occur, the feed becoming again normal as soon as the small jammed body has been conveyed past the rolls 1 and The result of thisis that the auxiliary roll l and the feed-r0112 rotatingat a higher speed than said roll 1 have the effect to cause any hiatus in the grain sheet that may appear in the direction in which the as this is clearly shown in Fig. 2. Thus, in

the arrangement described comprising the auxiliary roll 1, the feed-r0112 and the bridge 5, the feeding layer reaching the end a of the bridge 5 will be quite uniform. It will now be seen, that the uniform feeding layer is not spoiled and that the material is fed from the point-4L toward theentrance opening or nip between the millstones 7 as uniformly as possible. To this end the feedroil 3 is provided which rotates at astill greater speed than the first feed-roll 2, the material passing at the point t in the form of a thin layer from the bridge 5 onto said roll 4 which conveys it further and then discharges it at the point 6 of its circumference into the entrance angle of the millstones. In such an arrangement, the material is fed in a wholly uniform and uninterrupted manner in the form of a thin layer of fleece to the millstones 7, so that the latter are adapted to engage each single particle ofthe material and to grind it in the most effective manner.

The bridge 5 being inclined at an angle less than the angle of repose, of the mate rial being ground, the grain will not of itself slide across the bridge by gravity, but requires a slight impulse, obtained by its discharge from the rotating roll 2, to send it across the bridge, so that the separate grains will lie closer together toward the lower edge of the bridge, being temporarily arrested or retarded by the roll 3, which is adjacent the lower end of the bridge, or contacts with it at a point on its circumference below the crest of the roll and gives the grains a slight change of direction, lifting them and carrying them over the crest of the roll in a uniform sheet, thus positively taking the material from the end of the bridge and discharging it into the nip of the grinding rolls.

I am aware, that feeding devices comprismg the same elements in a different combiaccording to the present invention.

What I claim now as my invention is:

In a feed mechanism for grinding mills, a ribbed roll, an auxiliary roll cooperating therewith to permit the material to pass between them, an adjustable bridge receiving material from said ribbed roll, a discharge roll at the lower end of said bridge, and driving mechanism for driving said rolls, whereby the auxiliary roll will be rotated slower and the discharge roll faster than the ribbed roll.

In testimony that I claim the foregoing as my invention I have signed may name.

ERNST ROTH. 

